Ernst alfred nilsen



No. 750,036. PATENTED JAN. 19, 1904.

E. A. NILSEN.

SCREW PROPELLER. APPLICATION FILED JUNE 27. :1903.

N0 MODEL.

Witnesses: A 'IIlVBIltDI"? V BAlfnNilsan Attorneys f Patented January19, 1904.

PATENT OFFICE.

ERNST ALFRED NTLSEN, OF CHRISTIANIA, NORWAY- SCREW-PROPELLER.

SPECIFICATION forming part of Letters Patent No. 750,036, dated January19, 1904.

Application filed June 27, 1903.

represent so large a part of the screw-surface.

that complete channels are produced, which very efliciently control thedirection of the water. Propellers of this kind, so-calledchannel-propellers, I have employed very satisfactorily. On thesepropellers the blades,however, were exactly bent after a screw-surface,so that the pitch allover had a constant value.

The improvement in the present propeller constructionconsists thereinthat the blades of the channel-propeller near their front and rear edgesare given a somewhat greater bending than that corresponding to theexact screw-surface. Hereby the water is more efiiciently caught and isin a certain manner pressed through the channels with a velocity whichon account of the said bending of the blades always is increased andgreatest at the rear edge where the water escapes. I

My invention is illustrated in the accompanying drawings, in whichFigure 1 is a rear perspective View of the propeller. Fig. 2 is thepropeller in side elevation, and Fig. 3 is a section along the curvedline a b in Fig. 1.

In Fig. 2 the dotted line 1 2 indicates the exact screw-line. It is seenthat the outer edge of one of the blades at its middle part follows thisscrew-line exactly; but at certain points 3 and 4 the edge begins todiverge from the screw-line, being given a sharper bending, whichincreases toward both ends. ()n the part 3 4 thus the pitch of this edgeline is held constant, whereas the pitch is continuously increased from3 to 5 and from 4 to 6, the pitch being greatest at both ends near 5 and6, but in such a manner that in each separate radial line from any pointin the line 5 3 4 6 to the axis of rotation for the propeller the pitchis the same on all points of this cises on the water.

Serial No. 163,415. (No model.)

radial line. If, consequently, a section is taken along a line a 6having all its points located in the same distance from the axis, thenthe line 7 8 9, Fig. 3, which hereby is obtained will be exactly thesame as the line 10 3 5, only'decreased in the same proportion as thedistances between the axis and the lines a Z) and 5 1O 2, respectively.The point 3 in Fig. 2 therefore lies on the same radial line as thepoint 8 in Fig. 3. By this particular bending the blades at their endedges 11 obtain the shape like a spoon.

The propeller is assumed to rotate in direction of the arrows 12, Figs.1 and 2. Then the water will be caught by the front edges 13 of theblades and forced through the channels until the water at the middlepart 4 1O 3 of the blades has obtained a velocity corresponding to thepitch on this middle part. As soon as the water, however, has passed thepoint3 the pitch is beginning to increase and the water therefore fromsaid point will run with always increasing velocity until it at the rearedge 11, where the pitch is greatest, slips the propeller with thegreatest velocity and correspondingly greater propelling action on theship. It also, by considering the perspective view, Fig. 1, is easy toimagine the energic action which the rear part of the blades exer- Theaction of the propeller upon thewater consequently consists therein thatthe Water is uniformly accelerated through the channels and "issuccessively brought up to the full velocity.

That a considerably better result is obtained by such a propeller thanby propellers with quite constant pitch on all points of thebladesurfaces is clearly stated by the extensive practical experimentswhich I have done. The experiments state'that a channel-propeller actsconsiderably better than a usual screw-propeller, while a propellerconstructed according to my present invention further gives a betterresult than a usual channel-propeller with exactly the same maindimensions.

It is also understood withoutfurther explaining that quite the sameaction is obtained.

Either the present propeller runs forward orbackward.

Having now described my lnvention, what I claim as new, and desire tosecure by Letters Patent, is

A screw-propeller having blades, the middle portion of which is bentWith constant pitch as a screw, and the leading and rear portion ofWhich are bent inversely With a variable pitch, which increasescontinuously from the middle to the edges, Where the pitch is greatestand in such a manner that the blades are inversely symmetrical to middle1 axis.

In testimony whereof I have hereunto affiXed my signature, this 11th dayof June, 1903, in the presence of two Witnesses.

ERNST ALFRED NILSEN.

Vitnesses:

AXEL LAHN, RICHARD TROKKE.

